It is a problem in the area of suspension systems to provide a flexible support structure having two degrees of freedom of rotation about a desired point while minimizing any translational movement of the object being supported. Optical scanning systems are a typical example of a type of system which requires a flexible suspension system having a high scanning frequency. In scanning systems that use a mirror to rapidly scan back and forth across an angular excursion, suspension component friction must be kept to a minimum in order to permit a high scanning frequency. It is also desirable to provide rotational freedom about two orthogonal axes while minimizing translational movement of the mirror or other supported object.
Suspension systems for supporting fast steering mirrors have been developed that provide two degrees of rotational freedom. For example, U.S. Pat. No. 5,529,277, assigned to Ball Corporation, provides a suspension system that utilizes two perpendicular four-bar linkages coupled by a common plate to provide a translational-free flexible suspension having two rotational degrees of freedom about a desired point. One of the four-bar linkages is secured to a stationary “ground” structure, and the other is attached to the object to be supported, such as a mirror. In one embodiment, two links of each of the two four-bar linkages are constructed from spring steel flexure elements that are rigid in all directions except about the rotation axis. The flexure elements thus comprise “revolute joints”. Because the flexure elements function as spring hinges, no friction is encountered when the suspension is displaced or pivoted.
Scanning systems that use a mirror to rapidly scan back and forth across an angular excursion require that friction be kept to a minimum in order to permit a high scanning frequency. It is also desirable to provide rotational freedom about two orthogonal axes while minimizing translational movement of the mirror or other supported object. Prior suspension systems satisfy one or more of these requirements, but no prior system provides all of the features of the present system.